What You Do to Me
by Heroes Fly-Minho's Hero Limps
Summary: It all started with a sparring session and Kaminari's sex joke.


-I can't believe how long it's been since I've posted a new story! Life's been crazy lately. Anyway, this is my first fic for this fandom and I also posted it on my archive account:) I really hope you all like it, as I was worried about the characterization. It's always nerve wracking to start writing for a new fandom. Also, this is the first fic where I actually used the, y'know, F-word. I really couldn't think of any way to stick to Katsuki's character without having him saying it. I hope you don't mind (though if you're reading about him, you probably don't XD). Enjoy! And leave a review if you want! They honestly make me so happy :3-

Sometimes, Izuku thought, Kacchan could be stupid.

All right, perhaps stupid was a bit strong of a word. Izuku knew that he would never dare to call Katsuki that out loud. Saying something like that to his face was basically the same as attempting suicide. Izuku wanted to live to see his graduation, after all, so he was careful to keep his mouth shut.

Why was he even thinking this in the first place? Well, it was a rare one-on-one sparring day in Class 1-A and this time, the students were able to pick their opponents. Izuku had immediately been jumped on by a beaming Ochako, who seemed to be the only one in class not treating his Quirk like a nuclear bomb to be avoided at all costs. Izuku was happy; he and Ochako trained together well and even playfully, Ochako grabbing various heavy items in the training room and throwing them like they were nothing. (Izuku very nearly sent one out the window and prayed that his newfound control would last)

However, it was Katsuki's partner that was the problem. Katsuki chose Todoriki Shouto. Izuku didn't even bother to wonder why. Of course Katsuki wanted to take down the one person in the class who had proven themselves to be stronger, if not the strongest.

Izuku just really wished he hadn't. _I liked this sparring room_ , he thought gloomily, as another explosion rocked the floor, followed by the hiss of melting ice. Three benches were in smithereens, there were charred holes in the mats placed on the hard floor, and quite a few scorch marks traced the ceiling. He was also quite glad that U.A. didn't allow young children in, because the flow of profanity spilling out of Katsuki right now was bordering on toxic.

"You're doing great, Todoroki!" Kirishima yelled from his place next to Izuku. "Yes! That was awesome! C'mon, Bakugou, don't let him win _that_ easily!" The class had lined up along one wall to watch the latest match, and had gradually backed up against it as flying shards of ice and flame came too close for comfort.

"That was so cool!" Kirishima cheered again, as Todoroki sent coils of ice snaking up Katsuki's legs, eliciting a frustrated growl from the blonde. "Shouto really knows what he's doing, huh?"

"Kirishima, if you don't shut your fucking mouth, I will throw your ass right out this window!" Katsuki snarled.

Kirishima mumbled something at the insult, bottom lip pushing out in a pout. "He's getting real fired up," he remarked.

"Uh, yeah," Izuku agreed uneasily. "Maybe we shouldn't, um, distract him?" He grimaced at a twin set of booms, as Katsuki shattered the ice at his feet in a blast of fire and smoke.

"If we don't distract him, he might end up killing Todoroki," Kirishima returned. "Seriously, this guy is a freaking tank; doesn't anything stop him? Or shut him up?" he added wryly, following another litany of assorted curses and filthy words.

"No," Izuku answered.

"...no? Just no?"

Izuku's mouth quirked up in a sheepish half-smile, scratching the side of his head. "Erm, Kacchan's never been the type to be quiet."

"You can say that again," Kirishima commented over the sound of Katsuki stumbling to avoid a blast of heat from Shouto with a shouted, "motherFUCKER—!"

"You must know all about that, huh, Midoriya?" a new voice joked from Izuku's other side.

Puzzled, Izuku blinked up into Kaminari's amber eyes. He leaned against the wall next to him, arms crossed and expression teasing. "What does that mean?" Izuku asked innocently.

Kaminari flashed an amused grin. "Nothing," he shrugged. "Just that out of all of us, you probably know more about how _loud_ Bakugou can be."

Izuku continued to stare blankly, sensing that he missed something when Kirishima snorted. He really sensed that he'd missed something when Iida craned his neck to fix Kaminari with a withering look over his glasses. "Kaminari, was that a sex joke?" he asked, deadpan and sounding just the way a disapproving class representative should.

Splaying a hand over his chest, Kaminari gasped. "I'd never joke about sex!"

"Please just go back to watching the match..." Iida trailed off with an exasperated sigh.

"But things were just getting interesting," Kirishima whined, jokingly nudging Izuku in the arm.

It clicked in Izuku's mind and his face flushed red. "Wait, were you making a—a sex joke about me and Kacchan?"

"It wasn't a very good one, but I appreciate the effort," Kirishima added.

Kaminari rolled his eyes. "Gee, thanks."

"You made a sex joke about _me and Kacchan_?"

"You guys make it very easy to joke about."

"B—but we're not—! We don't even—!

"Oh for God's sake!" The exclamation came from Momo this time, as she leaned over from her end of the line in an angry flash of black hair. "Would you guys shut up? We're trying to pay attention and trust me, _nobody wants to hear about Midoriya's and Bakogou's sex life!"_

This, evidently, seemed to bring everyone's attention back to the match when Katsuki accidentally set off an explosion in his own face.

 _ **XxxxxxX**_

He should've known Katsuki wouldn't let a loss like that go.

It was late evening when Izuku ventured down to U.A.'s gym. The sparring room would've been his first choice on a boring afternoon, when he was looking for something to do and decided to train before sleeping. There was a lot of sturdier equipment in there. But since it was still in repair after the explosive match, he settled for the gym farther off in the building. Sighing, he twisted his fingers in the hem of his blue-and-red All Might T-shirt; one of his favorites.

 _Maybe I'll try the biggest weights today,_ he thought with an inner grin. _I wanna see if I can control One For All enough to just lift them. It's not like I'll be trying to hit anything, after all, so it might work better—_

His thoughts were cut off by a thundering bang from behind the gym's doors. Startled, he crept up to the heavy metal door and peeked through the narrow window. Inside was a blur of movement and a punching bag swinging in and out of view. Curious, Izuku planted a hand on the door and pushed his way inside.

The interior of the room was dimly lit by sunset, the lights shut off for some reason. He soon recognized that reason when the room was illuminated by a lightning-crack explosion. Jumping, he watched, wide-eyed, as Katsuki hurled himself at a punching bag twice his size."Half-and-half bastard!" the blonde growled, fist connecting with the bag in a way that made Izuku flinch. "Made me look like such a—" Breaking off with a low sound of rage, Katsuki sent the heel of his hand into the bag and detonated a blast that sent the whole thing rocking up into the ceiling. "Dammit!" It bounced off, swinging back faster, and he lunged for it.

Izuku gaped as the blonde delivered sets of punches with lethal speed and power. Worry filled him for Katsuki's hurt ego, but stirring behind that was awe. Katsuki moved like thunder and lightning, eyes alight and his shock of ashy blonde hair rumpled. A formfitting black tee showed off the power in his arms when he fought, the hard strength of him. Izuku caught himself watching the flex of muscle in Katsuki's back when he moved and shot his gaze down to his shoes. A heated blush threatened to rise in his face. _Don't stare._

Three more bone-rattling strikes and then nothing but the sound of them breathing. Then, "the fuck are you looking at, Deku?"

Izuku's gaze jerked up at once, meeting the smoldering wine-colored eyes across the room. Katsuki had his usual glare in place, backlit by the floor-to-ceiling windows. The sky had been stained orange this late and strands of flame painted the lines of his broad shoulders. "N—nothing!" Izuku stammered out, snapping himself out of his reverie. "I just came down to, uh, train a little. ...you?"

"What does it look like?" Katsuki asked drily. He turned away, examining his upturned hands and the tendrils of smoke drifting from them.

Uneasy, Izuku tried for a smile. "You're doing really good," he ventured. "Shouto had to take a long time to beat you."

"Yeah, but the asshole still beat me, didn't he?" Katsuki backed up the harsh words with another blow to the punching bag, the thump loud in the lonely room.

"You had a bad day," Izuku replied encouragingly. "And people were distracting you."

"Yeah, right."

"No, really. Kirishima kept talking and—"

"Jesus, does it look like I want your fucking pity?"

Clamping his mouth shut, Izuku took one look at Katsuki's scowl and shook his head. "Good," Katsuki snapped. "So shut the hell up." He glanced away, down at his hands, and Izuku thought he saw him wince. "Dammit."

Izuku blinked, curious and glad for a change of topic. Any time that he wasn't fighting with Katsuki (which was a rare time indeed) left him warm inside and he wanted to prolong it as much as possible. "What's wrong?"

"Nothing."

"But you're acting like your hands hurt."

"They don't."

"Kacchan, if you're hurt," Izuku began, sly but cautious at the same time, "you'll have a harder time beating Shouto next time. O—or me."

Katsuki's eyes narrowed. "Fuck you."

"Kacchan," Izuku sighed. He waited for a minute, but of course the hard look on Katsuki's face never changed. Shoulders sagging in defeat, he started to turn away. "Fine. Uh, I'll just...let you train then." He pressed his teeth together, trying to hide his frustration. Walking away wasn't easy for him, especially when he knew that he could help.

"...shit. Wait."

Izuku halted, glancing at Katsuki over his shoulder in surprise. Katsuki shifted his feet, fingers curling. "You know anything about how to fix this?" he asked gruffly, holding up a hand for inspection. The damage wasn't entirely visible, but the skin was reddened.

"I—Maybe," Izuku replied. "I mean, I know what to do when I'm tense and I think the muscles in your hands are the same way."

"Fine then." Katsuki's gaze dropped to the floor. After a second, he scowled up at Izuku again. "You coming over here or what?"

"Oh!" Izuku squeaked. "Yeah, okay." He crossed the room, glancing around and spotting a pair of chairs in the corner. "Can you bring one of those over here?"

"All right," Katsuki grumbled, like he was being asked to do something unfathomably difficult. He trudged over to Izuku and the two dragged two chairs over near the center of the room.

Izuku maneuvered them around to face each other, then pointed at one. Katsuki gave him his flattest _what the hell_ look. "You gotta sit down," Izuku explained.

His only reply was a grunt. But Katsuki plunked himself down in the chair, slouching like a spoiled prince on his throne and crossing his arms. He might've been trying his damnedest to look intimidating and Izuku didn't have the heart to tell him that the effect was ruined by the flame-print gym shorts he had on. He bit down on a rising smile as he took the chair across from Katsuki and shifted to perch on the edge of it. "Here," he said, offering up a hand.

Unfolding his arms, Katsuki held out his hand grudgingly. Izuku took it in his own and ghosted his thumbs over the palm, feeling callouses and heated skin; battle-hardened hands. His fingers curled around the softer skin at the back of Katsuki's palm and Izuku inhaled a steadying breath.

"So what's wrong with em?" Katsuki asked, voice holding an edge of iron.

"Um. I think they're just overworked. Probably all tensed up and irritated from using your Quirk so much." Izuku trailed his fingers down Katsuki's, coaxing his hand open.

"What're you gonna do abou—?" The question ended midway as Izuku placed his thumbs onto Katsuki's skin and pressed. Taken off-guard, Katsuki watched dumbly as Izuku's thumbs rubbed circles into his palm.

Izuku had to distract himself from the dark-cherry eyes searing into him, so he focused on the task at hand; he found the tensed muscles and set to working them loose. His thumbs ran along the lines of Katsuki's hand, sensing the heat beneath. Once he felt that he'd massaged the palm enough, he moved on to the fingers, working the pads of his thumbs up every one of them. He thought he heard a relieved exhale from Katsuki, but couldn't be sure. It still sent a smile playing across his lips.

"I think you work yourself too hard sometimes, Kacchan," Izuku ventured. He wanted to break the silence somehow, though he was still unsure about Katsuki's response.

It was, of course, the usual, "fuck you," but it was noticeably quieter, losing its bite. Izuku didn't let it bother him and moved his attention on to the next hand; lifting it into his grasp, he began to run his thumbs over the stressed muscles there. "Deku," Katsuki sighed, and dear god, he actually _sighed_ it.

Biting his lip, Izuku tried to control the blush he could feel rising in his face. It was just— He'd never seen Katsuki like this before, relaxing under Izuku's touch and almost slumping in his chair. He wondered if anyone else in U.A. had seen the fiery student with his guard down like this and it warmed his heart to think that he might be the only one.

"Almost done," he said under his breath, the pad of his right thumb running down Katsuki's ring finger.

"D'you do this to yourself? When you get stressed?" Katsuki asked. Izuku repressed a shudder at the relaxed blend of syllables.

"Sometimes," he replied. "But it's hard to reach my back and things like that, so sometimes I ask Ochako to help me."

Katsuki stilled almost imperceptibly. "Ochako?"

"Uh, yeah." Izuku wondered at the strange tilt to Katsuki's voice. It couldn't be jealousy...could it? Pushing the impossible idea from his mind, he let go of Katsuki's hand, having finished the massage. "There," he chirped. "That should help a little."

Katsuki's gaze shifted down to his hands laying palms-up in his lap, a strange expression on his face. For a moment, Izuku could've sworn that the blonde's eyes softened. Then they flicked up to Izuku's face, steely once again. Katsuki huffed out a frustrated sigh, raking a hand through his hair. "I hate you," he muttered.

Izuku blinked. "I—I'm sorry," he stammered, unsure as to why he felt the need to apologize.

Katsuki took one look at the innocent, green eyes fixed on him and growled under his breath. "I _hate_ you," he repeated in a quick breath, as he reached for Izuku's neckline and hauled him right off his chair.

Izuku yelped as he stumbled forward, forehead bumping Katsuki's a second before their lips met. He froze. Katsuki was... He was...

It was a hard fleeting kiss, a press of skin on skin, and then in a moment, it ended. Izuku stared in shock as Katsuki pulled back a fraction of an inch, those sin-red eyes slanted up at Izuku. With a tremble crawling up his spine, Izuku realized he'd caught himself on the edges of Katsuki's chair, caging him between his arms. He'd never been this close before. When he inhaled, he took in Katsuki's scent; he smelled like childhood, warmth, ash, hellfire, heaven.

"I...I thought you hated me," Izuku mumbled, fingertips touching his lips as though he wanted to keep the memory there.

"I do," Katsuki replied lowly. Then he moved just enough for their noses to brush together. His voice dropped. "I hate what you do to me."

Izuku couldn't breathe.

This wasn't real. This what he saw in the deepest of his dreams, that he never shared with anyone.

They didn't move for a long minute. Somewhere in that time, it built between them, that thing that Izuku couldn't name. It reminded him of Katsuki's explosions, right before they went off: heat like a struck match.

And then in a sudden rush, Izuku darted forward and crashed their lips together again. Katsuki growled in annoyance and at first, Izuku was terrified that he'd be pushed away. But he felt fingers card through his hair and curl in the back of it. "You kiss like a nerd," Katsuki murmured, reeling him in and angling his head. Their mouths slotted together and Izuku sighed. He even tastes like fire, he thought, when his teeth caught clumsily on Katsuki's lower lip. But there was a soft gasp and Katsuki's hands pulling him closer. His arms strained with the effort of holding his weight up on the chair, bent over Katsuki as he kissed the breath right from his lungs. But he didn't want to move, because that would mean ending this and this should never end.

Katsuki's mouth curved toward a smirk against Izuku's and he teasingly traced the line of Izuku's upper lip with his tongue. One For All activated in about half a second and Izuku jerked with a _crunch_ as the sides of Katsuki's chair cracked. Luckily, it hadn't broken entirely, but their kiss had and Katsuki was staring at him.

"Sorr—"

Katsuki's hands splayed at his lower back and yanked him into his lap. Izuku flushed, having never thought he'd be faced with straddling Katsuki in a chair, but Katsuki didn't give him room for embarrassment. He leaned up, lips finding Izuku's, and drawing a weak noise out of him. " _Kacchan_."

"I _hate_ —" Katsuki's teeth sank into Izuku's bottom lip, then drifted down to nip at his chin. "—that I can't really hate you." Another graze of teeth at Izuku's jaw and then they were traveling down his neck. Izuku sucked in a fast breath, fingers clinging to Katsuki's shoulders. His head fell back against his will as Katsuki kissed his way down his throat. He was rough, because of course he would be, occasionally biting down on pale freckled skin. But he never broke skin and Izuku's eyelids fluttered at the feeling of Katsuki's tongue soothing over the indents he left behind. He mouthed back up Izuku's neck, following the line of his jugular, until he reached his ear. Izuku felt lips close over his earlobe and suck, and he was moaning before he could stop himself. Katsuki's smug grin curled by his jawline.

He was having too much fun, Izuku decided. But he knew Katsuki too well and he bet he could find exactly what turned him on in no time. He brought his fingers up, sliding them into Katsuki's hair and along his scalp. Curling them, he pulled just right and Katsuki _whimpered_. And—god—he tipped his head back, baring his throat and the way his lashes sank low. Izuku would do anything if he got to see this again. He placed chaste kisses up along the arch of Katsuki's neck, until he reached his chin and felt him sigh. Trailing his nose down Katsuki's jaw, he breathed in that addictive scent again. "Kacchan," he rasped, and he smelled smoke.

Not the smokey tang from Katsuki's skin, but smoke, grey and swirling. He didn't have much time to feel the burst of heat. But when he did, it was at the small of his back, and it was only pleasant before it started to kinda hurt like hell.

Hissing, Izuku shot his hands down to grab Katsuki's wrists. "Kacch—"

"Shit," Katsuki snapped, realizing it at the same time and snatching his palms away. Frustration and concern warred in his expression. "You okay?"

"I think so..." Twisting, Izuku tried to peer at his back. He winced, because it stung. Jesus, what had Katsuki done to him?

"Um. Deku."

"What?" Glancing up, Izuku saw Katsuki pointing wryly at something behind him. He followed his gaze and saw the full-length mirrors at the end of the room. His ears burned pink. Oh. Two perfect handprints had been burned through the back of shirt and were outlined in red on the small of his back. He really hoped those wouldn't last a long time. "Ow." He said it accusingly, shooting Katsuki a dry look.

"Shut up, wimp," Katsuki returned, harsh but with a kiss placed on the juncture of Izuku's neck and shoulder. "It'll fade."

His tongue flicked against skin and Izuku shivered. "But until then, people might see it."

"What?" Katsuki glanced up with a devilish grin. "You don't like it?"

"Well, its obvious you do," Izuku mumbled, sheepish. Then he actually giggled, as Katsuki nuzzled at Izuku's hair.

"Damn right I do," he whispered. His fingertips trailed down Izuku's back, carefully avoiding the marks. "I want all of them to know who you belong to."

A smile playing at his lips, Izuku smoothed his fingers over Katsuki's hair. He felt Katuskis' hands playing at the hem of his shirt and remembered that these were the same hands that had hurt people before, that had hurt him before. A prickle of doubt made him frown. "D—did you mean it?" he asked. "Do you really have feelings for me or is this some...?"

Katsuki's eyes flashed. "I might say a lot of shit to you," he replied in a steely tone, "but I don't lie." Then the usual anger softened at the edges. "Deku, I know I hurt you, but—" Swallowing, he nosed his way into the crook of Izuku's neck and rested his head there. "I wanna make it up to you."

"You do?" Izuku asked, voice breathy with surprise and their closeness.

"Yeah. I mean, I like you." Katsuki's lips grazed the side of Izuku's throat. "Fuck, I really like you, Deku."

Izuku's smile widened and he pressed his cheek to the spiky fluff of Katsuki's hair. Tears stung his eyes, to think that he wouldn't have to worry about the abuse, the awful words. Katsuki felt the same way he felt. Katsuki felt the same. "Thank you," he murmured, and felt Katsuki hold him closer.

They sat in the dying sunlight together, content just to be in each other's presence.

Until, of course, the broken chair collapsed at last and Izuku landed very ungracefully on top of his new boyfriend.

Just the kind of start that could be expected of them.


End file.
